Field
The present disclosure relates generally to the field of lithium-ion batteries, and more particularly, to an electrolyte additive.
Background
Along with the rapid development of smart electronic products over recent years, increasingly high requirements have been imposed on the battery life of lithium-ion batteries. Developing high-voltage lithium-ion batteries is one effective way to improve the energy density of lithium-ion batteries.
At present, lithium-ion batteries with working voltage above 4.35 V have become a hot research topic of numerous research institutes and businesses. At a high voltage, however, oxidative activity increases and stability decreases for the materials forming the positive electrode (cathode). Increased oxidative activity and decreased stability may cause a non-aqueous electrolyte to undergo electrochemical oxidation on the positive electrode surface and then to decompose to produce gases. At the same time, transition metal elements (e.g. nickel, cobalt, manganese, etc.) in the materials forming the positive electrode (cathode) may undergo reduction reaction and dissolve out, causing electrochemical properties of the lithium-ion battery to deteriorate further. At present, the main solution is to add a film-forming additive into the electrolyte. Such an additive can form a film on the positive electrode, which, however, may cause the interface resistance to increase, leading to decreased migration and diffusion kinetic capability of lithium-ions in the battery, and further to a decayed C-rate (charge and discharge rates) and cycle performance of the battery. For example, the film-forming additive may cause the discharge rate to decrease, which is to say that if we use the same discharge rate, it can cause lower capacity.
As a result, there is a need for developing an electrolyte additive that enables the lithium-ion battery to maintain a good cycle life, low-temperature discharge characteristics, and high-temperature storage characteristics even at a high voltage.